Nucleon effective mass effects on the Pauli-blocking function

Abstract

The effects of nucleon effective mass on the Pauli-blocking function are worked out. We have shown that such effects on the quasi-deuteron mechanism of photonuclear absorption are rather relevant. The Pauli-blocking function has been evaluated by applying a Monte Carlo calculation particularly suitable for simulation of intranuclear cascade processes of intermediate-energy nuclear reactions. The nucleon binding in the photonuclear absorption mechanism is taken into account accordingly.

Level density parameter at the fission saddle point from intermediate-energy photofission cross section data

“…This is equivalent to saying that fissility for 237 Np is equal to unity and independent of incident energy. By combining (2)-( 4), and taking the photofission cross section data in the 3)), and the shaded region is the associated uncertainty; the dashed-line represents the prediction by Chadwick et al [56], and full squares are the results by the Monte Carlo calculation by de Pina et al [57]. The curve in (b) represents σ T a (E γ ) defined by equation (5) in the text, and the shaded area is the associated uncertainty.…”

“…The semiempirical Pauli-blocking function obtained as described above is represented in figure 1(a) (full line with uncertainties given by the shaded area). To allow a comparison, also shown are the theoretical predictions by Chadwick et al [56] (dashed-line), and the results of a Monte Carlo calculation by de Pina et al [57] (full squares). It is seen that the agreement can be considered satisfactory (within less than ∼10%) at energies up to about 80 MeV.…”

Photonuclear reactions at intermediate energies investigated via the Monte Carlo multicollisional intranuclear cascade model

“…The competition between blocked and nonblocked events is directly related to the phase-space reduction due to the Pauli-blocking mechanism, and is a consistent way to determine the Pauli-blocking function for a given target and photon energy. This procedure is somewhat at variance with the one reported in a recent work [39], where the nucleons effective masses are left as free parameters and the sorting procedure does not take into account relative momentum correlations. In Fig.…”

Fissility of actinide nuclei by 60-130 MeV photons

“…(2,3), and by making use of the experimental data of σ f for 237 Np (Table 1, 10 th column), the Pauli block function in the incident photon energy range 60-130 MeV, can be expressed as This result is shown in Fig.1-b (straight line) together with the semiempirical values of f B (circles). For a comparison, the results of a Monte Carlo calculation (full squares in Fig.1-b) obtained by de Pina et al [19] is also shown. Except for 129 MeV, the above results differ from each other by 8% on the average.…”

“…Finally, f B (E γ ) is the Pauli block function, which can be established in a semiempirical way, if we observe that, among the actinide nuclei which have been investigated , 237 Np is the one which has a low fission barrier (4.63 MeV, therefore, a good chance for fission) and, at the same time, the greater neutron separation energy (6.58 MeV). Thus, we can assume that the photofission cross section of 237 Np represents its total photoabsorption cross section, i.e., (4)); full squares are results from a Monte Carlo calculation [19]; c) total nuclear photoabsorption cross section for actinide nuclei as given by Eq. (15); the shaded area indicates the uncertainties ( estimated to ± 5%).…”